JP2005291757A - Residual chlorine sensor, residual chlorine meter using it and residual chlorine sensor manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a residual chlorine sensor constituted so as to prevent that the life of electrodes becomes short by the elution of silver chloride and silver chloride is simply peeled by collision and capable of extending the life of the electrodes, a residual chlorine meter using it and a residual chlorine sensor manufacturing method. <P>SOLUTION: The residual chlorine sensor 1 has an anode 10 and a cathode 11 and is constituted so as to measure the current flowing across both electrodes 10 and 11 by oxidation-reduction reaction to measure residual chlorine in a solution. The anode 10 is constituteed by forming a coating layer 20 comprising an eutectic salt of silver sulfate and silver chloride on the surface of an electrode body 19. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a residual chlorine sensor, a residual chlorine meter using the same, and a method for manufacturing a residual chlorine sensor.

  Water used in tap water and other industrial water, industrial wastewater, swimming pools, public baths, etc., is sterilized by sodium hypochlorite. However, excessive use of sodium hypochlorite increases the amount of residual chlorine and generates carcinogenic trihalomethane, so it is necessary to monitor the amount of residual chlorine.

  As a method for measuring residual chlorine, the orthotolidine method for visually confirming the color change caused by the reaction of residual chlorine with a hydrochloric acid solution of orthotolidine, or the residual chlorine reacts with diethyl-p-phenylenediamine (DPD). There is a DPD method for confirming the color change that occurs, but since it is necessary to use a reagent for each, not only the running cost is required, but in continuous measurement, a means for weighing the reagent and adding a certain amount is required, Deviceization was difficult.

Therefore, a polarographic residual chlorine meter that measures the residual chlorine concentration by immersing the electrodes in the test solution and measuring the current flowing between the electrodes has come to be used. This polarographic residual chlorine meter has a cathode electrode (working electrode) made of gold or platinum in the test solution and an anode electrode (counter electrode) formed by forming a silver chloride thin film on silver. Is applied to cause an electrode reaction represented by the following expression on the anode electrode side and the cathode electrode side, and the residual chlorine concentration is measured using the magnitude of the current flowing at this time.
2Ag → 2Ag ⁺ + 2e ⁻
HClO + H ⁺ + 2e ⁻ → H ₂ O + Cl ⁻ or
Cl ₂ + 2e ⁻ → 2Cl ⁻ (under acidity)
ClO ⁻ + 2H ⁺ + 2e ⁻ → H ₂ O + Cl ⁻ (under alkali)

In the polarographic residual chlorine meter, the anode electrode needs to have a surface area several tens of times larger than that of the cathode electrode. Therefore, conventionally, for example, a thin silver wire having a diameter of about 0.3 mm is spirally wound as an anode electrode, and then silver chloride is plated on the silver wire by electrolytic treatment or the like.
JP 62-43556 A

  However, when silver chloride is coated on the silver wire by the electroplating method, since the silver chloride has a resistivity close to that of the insulator, the plating coating is completed with the thin silver chloride formed, There was a problem that silver chloride could not be coated thickly. Further, since silver chloride on the anode side gradually dissolves (elutes) when measuring the concentration of residual chlorine, there is a problem that the thinner the silver chloride layer, the shorter the life of the electrode. Furthermore, since the silver chloride layer is extremely thin, the coating layer may be peeled off immediately by collision with the outside during transportation or use, and when silver wire is exposed, it is further exposed to silver electrochloride by a local electrolysis (battery) reaction. There was a problem that dissolution of the electrode was promoted.

  In addition, since silver chloride is a photoreceptor, it is easily affected by light (particularly ultraviolet rays), and responds slightly to ultraviolet rays from indoor fluorescent lamps, and its electromotive force may fluctuate. In addition, when used outdoors, the measurement value may change significantly due to ultraviolet light contained in sunlight. In particular, when used outdoors, the influence of ultraviolet light may appear greatly during maintenance.

  In Patent Document 1, in a silver electrode for an enzyme electrode using platinum as an anode electrode and silver as a cathode electrode, a silver powder, a mixture of silver chloride and silver sulfide, and an epoxy resin are mixed and stirred, and then pressure-molded. The configuration is shown. However, in such a configuration, it is difficult to make the size (particle size) of the silver powder constant or to distribute the silver powder uniformly in the epoxy resin, so it is difficult to stabilize the performance of the cathode electrode.

  The present invention has been made in consideration of the above-mentioned matters. The purpose of the present invention is to prevent the electrode life from being shortened by elution of silver chloride or to prevent the silver chloride from peeling off easily by collision. The present invention provides a residual chlorine sensor, a residual chlorine meter using the same, and a method for manufacturing a residual chlorine sensor.

  In order to achieve the above object, a residual chlorine sensor according to claim 1 has an anode electrode and a cathode electrode, and measures the current flowing between the two electrodes by an oxidation-reduction reaction, thereby measuring residual chlorine in the solution. A residual chlorine sensor to be measured has an anode electrode in which a coating layer made of a eutectic salt of silver sulfide and silver chloride is formed on the surface of an electrode body.

  The silver sulfide contained in the eutectic salt may have a weight of 5 to 30% (Claim 2).

  The shape of the electrode body may be substantially cylindrical.

  The surface of the coating layer may be roughened (Claim 4).

  The residual chlorine meter according to claim 5 obtains residual chlorine from the residual chlorine sensor according to any one of claims 1 to 4 and the magnitude of current flowing between the anode electrode and the cathode electrode of the residual chlorine sensor. It has an arithmetic processing part and a result output part which outputs the measurement result of residual chlorine.

  The method for producing a residual chlorine sensor according to claim 6 is obtained by mixing 5-30% by weight of silver sulfide with silver chloride, immersing the electrode body in a eutectic salt obtained by melting the mixture, and pulling it up. The surface of the electrode body is coated with a eutectic salt of silver sulfide and silver chloride.

  In the residual chlorine sensor according to claim 1, since the resistivity can be set appropriately and the coating layer can be formed sufficiently thick with a eutectic salt of silver sulfide and silver chloride, Shortening of the lifetime of the residual chlorine sensor can be suppressed. That is, it is possible to prevent the residual chlorine sensor from being deteriorated and perform good measurement over a long period of time. Even if the coating layer collides with something at the time of measurement or transportation, the silver chloride coating layer is not easily peeled off. That is, it is possible to provide a residual chlorine sensor that is easy to handle and can always perform stable measurements.

  The metal constituting the electrode body is preferably silver in order to improve the fusion with the eutectic salt and stabilize the electrode potential. Moreover, in order to make the joining property in the joint surface of an electrode main body and eutectic salt favorable, it is preferable that the joint surface with the eutectic salt of an electrode main body is roughened.

  In addition, when the weight of the silver sulfide contained in the eutectic salt is 5 to 30% (Claim 2), the silver sulfide having a weight of 5% or more contained in the eutectic salt effectively absorbs ultraviolet light. Since it can absorb, even if the residual chlorine sensor is exposed to ultraviolet rays, silver chloride does not cause an electrode reaction, and stable measurement can be performed. Moreover, since the weight of silver sulfide is 30% or less, it is possible to prevent the resistivity of the residual chlorine sensor from being lowered by the semiconductive silver sulfide. The weight of silver sulfide contained in the eutectic salt is preferably 10 to 20%, and optimally around 16%. Further, the eutectic salt of silver sulfide and silver chloride mixed at the above mixing ratio can obtain a good resistivity of about 5 Ωm.

  When the shape of the electrode body is substantially cylindrical (Claim 3), a sufficient surface area can be obtained on the surface of the electrode body, and processing is easy. In other words, the thin silver wire wound in a spiral manner as in the conventional anode electrode, it is difficult to process such as immersing in the melted eutectic salt of silver sulfide and silver chloride, but the shape of the electrode body is If it is cylindrical, even if it receives heat from the melted eutectic salt, its shape does not easily distort.

  When the surface of the coating layer is roughened (Claim 4), the contact area between the residual chlorine sensor and the test solution can be increased, so that a sufficient reduction reaction is given to the cathode. be able to.

  Since the residual chlorine meter according to claim 5 can extend the life of the electrode by using the residual chlorine sensor according to any one of claims 1 to 4, the residual chlorine sensor can be used over a long period of time. Maintenance free. Further, the coating layer of the residual chlorine sensor is thick and is not easily peeled off, so that the handling becomes easy.

  According to the method for manufacturing the residual chlorine sensor according to the sixth aspect, the thickness of the eutectic salt layer coated on the electrode body can be freely set. That is, the thickness of this coating layer is the temperature of the melted eutectic salt, the time for which the electrode body is immersed in the melted eutectic salt, the speed at which the electrode body is pulled up from the melted eutectic salt, and the electrode body Can be freely set according to the number of times of immersion in the eutectic salt. In particular, by forming a thick eutectic salt coating layer on the electrode body, a residual chlorine sensor having a long life and excellent durability can be produced.

  Further, if the mixture of silver sulfide is about 5 to 30% with respect to silver chloride, an increase in the melting point of the eutectic salt can be suppressed, and coating processing of the eutectic salt on the electrode body becomes easy. The optimum weight of silver sulfide contained in the eutectic salt is about 16%. Furthermore, since silver sulfide has the property of absorbing light, the electromotive force does not fluctuate due to external light hitting silver chloride and the measured value is stabilized. In addition, a eutectic salt in which 5 to 30% by weight of semiconductor silver sulfide is mixed with substantially insulative silver chloride has an appropriate resistivity (about 5 Ωm). Even if it is formed to be sufficiently thick, a current necessary for measurement can be passed, so that accurate measurement can be performed.

  In addition, it is possible to improve the fusion between the electrode body and the eutectic salt by attaching the eutectic salt to the roughened surface after the surface of the electrode body is roughened. By roughening the surface of the eutectic salt formed on the surface of the electrode body, the surface area of the anode electrode can be increased.

  FIGS. 1 and 2 are views for explaining a first embodiment of the present invention. FIG. 1 shows a configuration of a residual chlorine sensor 1 of the first embodiment and a residual chlorine meter 2 using the residual chlorine sensor 1. FIG. 2 and FIG. 2 are diagrams for explaining the configuration of the residual chlorine sensor 1.

  1, 3 is a residual chlorine meter main body, 4 is a display unit of the residual chlorine meter main body 3, 5 is an operation unit, and 6 is a residual chlorine sensor 1 that is detachably connected to the residual chlorine meter main body 3. It is a connector to do. On the other hand, the residual chlorine sensor 1 is connected to the sensor main body 7, a signal line 9 having a connector 8 configured to be connectable to the connector 6, and the residual chlorine meter main body 3 via these connectors 6, 8 and the signal line 9. It has the anode electrode 10 and the cathode electrode 11 which are connected. Reference numeral 3a denotes an arithmetic processing unit for obtaining residual chlorine from the magnitude of the current flowing between the electrodes 10 and 11, and the display unit 4 is an example of a result output unit for outputting a measurement result of residual chlorine. Note that the result of residual chlorine is not limited to the display output shown in this example, but the measurement result may be printed or output as data to a higher-level information processing apparatus.

  In the enlarged view of the main part shown in FIG. 2, the sensor body 7 has a plurality of concentric circular cylinders 12 to 15 that are thin at the distal end 7a and thick at the proximal end 7b, for example, as shown by a two-dot chain line. It is the cylinder which consists of a synthetic resin of the shape which has the external shape which connected. In addition, the electrode tip 16 made of gold is fixed to the tip end portion 7a of the sensor body 7 so as to protrude from the tip end of the cylindrical body 12, and the electrode tip 16 is held watertight. Reference numeral 17 denotes a lead wire electrically connected to the electrode chip 16, and reference numeral 18 denotes a connection portion between the lead wire 17 and the electrode chip 16. That is, the cathode electrode 11 of the present embodiment includes, for example, the electrode chip 16, the lead wire 17, and the connection portion 18.

  On the other hand, the anode electrode 10 includes an electrode body 19 made of substantially cylindrical silver, a coating layer 20 covering the surface of the electrode body 19, a lead wire 21 electrically connected to the electrode body 19, and a connection thereof. Part 22. The anode electrode 10 is flush with the outer peripheral surface of the cylindrical body 13 and is watertightly attached so that water from the outside does not enter the sensor body 7. In addition, the coating layer 20 is obtained by solidifying a silver sulfide and silver chloride eutectic salt after adhering by the procedure described later, and the area of the outer surface (a wetted part) 20a is the outer surface of the electrode chip 16. It is configured to be several tens of times larger than the liquid contact portion 16a.

  In the anode electrode 10 of the present embodiment, an electrode exposed portion 19a where the coating layer 20 is not applied is formed on the upper end portion of the electrode body 19, and this electrode exposed portion 19a is watertight from the outside (electrically) by the cylindrical body 14. The connecting portion 22 of the lead wire 21 is formed in the electrode exposed portion 19a. The lead wires 17 and 21 are connected to the residual chlorine meter main body 3 in a state where they are cut off from the outside as the signal wires 9 and are insulatively coated so as not to be in electrical contact with each other.

  Therefore, by immersing the residual chlorine sensor 1 of the present embodiment in a test liquid such as drinking water, the liquid contact portions 20a and 16a of both electrodes 10 and 11 can be brought into contact with the test liquid. The current flowing between the liquid portions 20a and 16a can be measured on the residual chlorine meter main body 3 side, whereby the residual chlorine concentration can be measured.

  FIG. 3 is a diagram for explaining a method of manufacturing the anode electrode 10 of the residual chlorine sensor 1. In FIG. 3, 30 is an electric furnace, 31 is a heater of the electric furnace 30, 32 is a crucible, and 33 is a eutectic salt of silver sulfide and silver chloride charged into the crucible 32.

  The mixing ratio of silver chloride and silver sulfide is preferably between 95: 5 and 70:30 by weight. That is, when the mixing ratio of silver sulfide is 5% or less by weight, the color of the mixture becomes too thin to absorb ultraviolet rays sufficiently, so that an electrode reaction may occur in silver chloride when exposed to ultraviolet rays. This is not preferable because of its properties. On the contrary, if the mixing ratio of silver sulfide of the semiconductor is basically 30% or more by weight, the resistance value of the coating layer 20 formed thereby becomes too low, so the residual chlorine concentration cannot be measured properly. It is not preferable.

  The mixing ratio of silver chloride and silver sulfide is more preferably between 90:10 and 80:20 by weight, so that the ultraviolet rays are sufficiently absorbed by the silver sulfide and the coating layer 20 has an appropriate resistivity. It is good as an electrode of a residual chlorine sensor. The optimum mixing ratio of silver chloride and silver sulfide is about 84:16 by weight, and the coating layer 20 formed of this eutectic salt has a resistivity of about 5 Ωm.

  The following example shows an example of mixing silver chloride and silver sulfide under this optimum condition. That is, 84% by weight of silver chloride and 16% by weight of silver sulfide are separately weighed and mixed by stirring to form a mixture. Then, this mixture is put into the crucible 32, and the crucible 32 is heated by the heater 31 so that the temperature is adjusted to, for example, 495 ° C.

  If the eutectic salt 33 is completely dissolved and impurities remain on its surface, it is removed using a glass rod or the like. As a result, the dissolved eutectic salt 33 (dissolved salt) is completed.

  On the other hand, the surface 19b of the cylindrical electrode body 19 made of silver is subjected to a rough surface treatment such as a sandblast treatment to increase its surface area. Next, the electrode body 19 is dipped in the dissolved salt 33 (dipping), whereby the surface 19b of the electrode body 19 is subjected to dip coating with the eutectic salt 33 to form the coating layer 20. .

  At this time, the surface 19b of the electrode body 19 is roughened, so that fusion at the contact surface between the electrode body 19 and the eutectic salt 33 can be performed firmly. Moreover, the electrode exposed portion 19 a can be formed by not immersing the upper end portion of the electrode body 19 in the dissolved salt 33.

  In the dip coating, the temperature of the eutectic salt 33 is related to its viscosity, and the thick coating layer 20 can be formed by setting the temperature above the melting point and low. In addition, the thickness of the coating layer 20 can be arbitrarily set by controlling the time and the number of times such as immersing the electrode body 19 in the eutectic salt 33 a plurality of times.

  In addition, when the electrode main body 19 is immersed in the eutectic salt 33 for the first time, it is preferable that the electrode main body 19 is immersed for a relatively long time to firmly bond the joint between the electrode main body 19 and the coating layer 20. In addition, the metal constituting the electrode body 19 may be basically anything, but is silver in order to ensure fusion with the eutectic salt 33 and suppress the generation of the interface potential at the critical plane. Is preferred.

  When the dip coating of the coating layer 20 is completed, the surface of the coating layer 20 is roughened by sandblasting or the like, so that the area of the liquid contact portion 20a can be increased.

  4 and 5 are diagrams showing modifications of the residual chlorine sensor. The difference between the residual chlorine sensor 1 ′ shown in FIG. 4 and the residual chlorine sensor 1 shown in FIGS. 1 to 3 is that the electrode body 40 constituting the anode electrode 10 ′ spirals a thin silver wire having a diameter of about 0.3 mm, for example. It is a point that is wound around. In addition, a coating layer 41 is formed on the surface of the electrode body 40 by solidifying the eutectic salt of silver sulfide and silver chloride after adhering.

  The electrode body 40 is formed with a coating layer 41 and then spirally wound around the cylinder 13 to form a substantially cylindrical outer shape as a whole. Further, by forming the anode electrode 10 ′ by winding a thin silver wire as in this example, a large number of irregularities can be formed in the liquid contact portion 41a of the coating layer 41, and thereby the surface area of the liquid contact portion 41a. Can be widened. Reference numeral 42 denotes a resin mold for preventing liquid from entering between the liquid contact portion 41a of the anode electrode 10 'and the cylinders 13 and 14.

  In addition, although the present Example shows the example which comprises the connection part 22 which connects the lead wire 20 with respect to the silver wire exposed part 40a of the electrode main body 40, this invention does not limit this structure, and an electrode Needless to say, the silver wire as the main body 40 may be extended as it is and used as the lead wire 20.

  FIG. 5 is a diagram related to the method of manufacturing the anode electrode 10 ′, and the method of manufacturing the residual chlorine sensor 1 ′ described using FIG. 5 is the same as the method of manufacturing the residual chlorine sensor 1 described using FIG. Although it is substantially the same, it differs in that the shape of the electrode body 40 immersed in the dissolved eutectic salt 33 is a thread-like silver wire. In addition, the electrode main body 40 of this example can also make the fusion | melting of eutectic salt with the electrode main body 40 more reliable by roughening the surface 40b by sandblasting etc. FIG. Similarly, the wetted part 41a of the formed coating layer 41 is also subjected to a rough surface treatment, so that the wetted part 41a and the test liquid to be measured can be more reliably joined to each other with accuracy. Measurements can be made.

  In addition, in each of the examples described above, the present invention has been described by showing a polarographic residual chlorine sensor. However, the residual chlorine sensor of the present invention may be based on a galvanic cell method. Moreover, although the example which connects the residual chlorine sensor 1,1 'to the handy type residual chlorine meter main body 3 is shown as an example of the residual chlorine meter 2, this invention is what the structure of the residual chlorine meter main body 3 mentioned above. It is not limited to being. That is, the residual chlorine sensor 1, 1 'of the present invention may be incorporated in a stationary analyzer that measures residual chlorine in the test solution. In particular, when tap water (clean water) is used as a test solution, sensors for measuring not only residual chlorine concentration of water but also turbidity, chromaticity, pH, and conductivity are arranged side by side. Although it is conceivable to configure a water quality analyzer as a water supply monitoring system that performs comprehensive management (evaluation) of water using the output from each sensor, such a comprehensive water quality analyzer is also considered to be a residual water analyzer according to the present invention. One of the chlorine meter 2.

It is a figure which shows the structure of the residual chlorine meter of this invention. It is a figure which shows the structure of the residual chlorine sensor used for the said residual chlorine meter. It is a figure explaining the manufacturing method of the said residual chlorine sensor. It is a figure which shows the modification of the said residual chlorine sensor. It is a figure explaining the manufacturing method of the said residual chlorine sensor.

Explanation of symbols

1,1 'Residual chlorine sensor 2 Residual chlorine meter 3a Arithmetic processing part 4 Result output part (display part)
10, 10 'Anode electrode 11 Cathode electrode 19, 40 Electrode body 19b, 40b Electrode body surface 20, 41 Coating layer 20a, 41a Wetted part (coating layer surface)
33 Eutectic salt

Claims (6)

  A residual chlorine sensor having an anode electrode and a cathode electrode and measuring residual chlorine in a solution by measuring a current flowing between both electrodes by an oxidation-reduction reaction, wherein silver sulfide and silver chloride are formed on the surface of the electrode body. A residual chlorine sensor comprising an anode electrode on which a coating layer made of a eutectic salt is formed.   The residual chlorine sensor according to claim 1, wherein the weight of silver sulfide contained in the eutectic salt is 5 to 30%.   The residual chlorine sensor according to claim 1 or 2, wherein the electrode body has a substantially cylindrical shape.   The residual chlorine sensor according to claim 1, wherein a surface of the coating layer is roughened.   A residual chlorine sensor according to any one of claims 1 to 4, an arithmetic processing unit for obtaining residual chlorine from the magnitude of a current flowing between an anode electrode and a cathode electrode of the residual chlorine sensor, and a measurement result of the residual chlorine A residual chlorine meter comprising a result output unit for outputting.   5-30% by weight of silver sulfide is mixed with silver chloride, and the electrode body is dipped in a eutectic salt obtained by melting this mixture and pulled up, so that the surface of the electrode body is a eutectic salt of silver sulfide and silver chloride. A method for producing a residual chlorine sensor, characterized in that the coating is performed by:

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